Paint sprayers and other devices utilize electric motors to rotate a shaft. In the case of paint sprayers, the shaft is sometimes connected to a crankshaft or cam/eccentric to translate the rotational motion of the shaft into a reciprocating motion. The reciprocating motion is transferred to a pump and used to increase system pressure in the paint sprayer. This pressure is used by the paint sprayer to spray and apply paint. Once the system pressure has increased to or above a maximum or stall pressure, the electric motor is powered off. As the paint is sprayed, the system pressure in the paint sprayer drops. Once the system pressure has decreased to or below a designated level, the electric motor is powered back on to resupply the paint sprayer with maximum pressure. In some paint spraying systems, the electric motor that supplies pressure to the paint sprayer operates solely based on the paint sprayer system pressure and doesn't “know” when an operator starts and stops spraying paint.
A cooling device is needed to keep the electric motor from exceeding its temperature rating during use. In some cases, a fan is connected to the shaft rotated by the electric motor and provides cooling air to the electric motor by drawing air through and/or around the motor. Depending on the configuration and parameters of the paint spraying operation, the electric motor can be powered on and off frequently, often more frequently than the number of trigger presses an operator makes with a spraygun. Frequently powering the electric motor off and on increases the heat rise and temperature of the electric motor. Fans that are directly connected to the shaft rotate only when the electric motor is powered. These configurations are designed to provide adequate cooling at maximum power/maximum air flow, but do not always provide enough cooling to the electric motor when frequent starting and stopping cycles are used. In other cases, thermostatically or electrically controlled clutches allow the fan to continue to provide cooling when the electric motor is not receiving power. Alternatively, independently powered fans can provide cooling to the electric motor. In the latter two cases, these additional components increase system cost and complexity.